This invention relates, in general, to bleaching and laundering compositions and their application to laundering operations. More specifically, this invention relates to bleaching and laundering compositions containing monoperoxyphthalic acid and/or a water-soluble salt thereof in combination with a chelating agent capable of forming a water-soluble metal complex in aqueous solution.
Bleaching compositions which release active oxygen in the laundry solution are extensively described in the prior art and commonly used in laundering operations. In general, such bleaching compositions contain peroxygen compounds, such as, perborates, percarbonates, perphosphates and the like which promote the bleaching activity by forming hydrogen peroxide in aqueous solution. A major drawback attendant to the use of such peroxygen compounds is that they are optimally effective at the relatively low washing temperatures employed in most household washing machines in the United States, i.e., temperatures in the range of 80.degree. to 130.degree. F. By way of comparison, European wash temperatures are generally substantially higher extending over a range, typically, from 90.degree. to 200.degree. F. However, even in Europe and those other countries which generally presently employ near boiling washing temperatures, there is a trend towards lower temperature laundering.
In an effort to enhance the bleaching activity of peroxygen bleaches, the prior art has employed materials called activators in combination with the peroxygen compounds. It is generally believed that the interaction of the peroxygen compound and the activator results in the formation of a peroxyacid which is the active species for bleaching. Numerous compounds have been proposed in the art as activators for peroxygen bleaches among which are included carboxylic acid anhydrides such as those disclosed in U.S. Pat. Nos. 3,928,775; 3,338,839; and 3,352,634; carboxylic esters such as disclosed in U.S. Pat. No. 2,995,905; N-acyl compounds such as those described in U.S. Pat. Nos. 3,912,648 and 3,919,102; cyanomines such as described in U.S. Pat. No. 4,199,466; and acyl sulfoamides such as disclosed in U.S. Pat. No. 3,245,913.
Pre-formed peroxyacids have also been used to effect bleaching in laundry wash solutions. U.S. Pat. Nos. 3,770,816; 4,170,453; and 4,259,201 are illustrative of prior art disclosures relating to bleaching compositions comprising a peroxyacid compound.
It is generally recognized in the art that metal ions are capable of acting as decomposition catalysts for inorganic peroxygen compounds and organic peroxyacids. In an effort to stabilize such bleaching species in the wash solution, chelating agents have been incorporated into bleaching detergent compositions. U.S. Pat. No. 3,243,378 to Stoltz, for example, discloses a bleaching composition containing a peroxygen bleaching compound and a chelating agent to sequester metal cations. In general, the chelating agents which have been used for this purpose fall into one of two categories: (a) materials such as heterocyclics compounds and ketones, notably 8-hydroxyquinoline, which tie up metal cations in the laundry wash by precipitating them from solution; and (b) materials such as aminopolycarboxylates and aminopolyphosphonate compounds which form water-soluble metal complexes with the cations present in the wash solution. Accordingly, U.S. Pat. No. 4,005,029 discloses that selected aldehydes, ketones and compounds which yield aldehydes or ketones in aqueous solution (e.g., 8-hydroxyquinoline) can be used to activate aliphatic peroxyacids, such as, diperazelaic acid, diperadipic acid and aromatic peroxyacids (and water-soluble salts thereof) including monoperoxyphthalic acid and diperoxyterephthalic acid. In U.S. Pat. No. 4,170,453, a mixture of 8-hydroxyquinoline, phosphoric acid and sodium pyrophosphate is disclosed as a preferred chelating system to stabilize the active oxygen generated in wash solutions containing diperoxydodecandioic acid, U.S. Pat. No. 4,225,452 to Leigh discloses the combination of specified classes of chelating agents (among which are phosphonate compounds) with inorganic peroxygen compounds and an organic activator for the purpose of suppressing the decomposition of the peroxygen compound in the bleach composition. Specifically, the chelating agent is said to inhibit the unwanted side reaction of the peroxygen compound with the peroxyacid formed by the primary reaction of the peroxygen compound and the activator, the effect of the side reaction being to deplete the peroxyacid bleaching species from solution. The Leigh patent, however, discourages the use of such chelating agents in solutions wherein the peroxyacid has a double bond between the carbon atoms in the .alpha.,.alpha.' position to the carbonyl group. Specifically, at column 2 of the patent, beginning at line 63, the patentee excludes phthalic anhydride as an activator for the disclosed bleaching composition because of instability. Inasmuch as the peroxyacid formed by the reaction of phthalic anhydride and an inorganic peroxygen compound is monoperoxyphthalic acid, the Leigh patent apparently discourages the use of monoperoxyphthalic acid in the bleaching compositions of the patent.
European Patent Publication No. 0,027,693, published Apr. 29, 1981, discloses the use of magnesium monoperoxyphthalate as an effective bleaching agent. There is also disclosed the optional combination of a bleaching agent with an "aldehyde or ketone peroxyacid activator as described in U.S. Pat. No. 4,005,029, e.g., 8-hydroxyquinoline which is a known peroxygen stabilizer". The Publication also discloses organic phosphonate compounds, along with a wide variety of other compounds, as being useful detergent builders which optionally may be included in the described washing compositions. No disclosure is made, however, concerning the beneficial effects attendant to the use of a small amount of organic phosphonate compounds to serve as chelating agents in bleaching compositions and particularly, in compositions containing magnesium monoperoxyphthalate.
Thus, while the art has concerned itself with improving the stability of peroxygen and peroxyacid bleaching compounds with the use of chelating agents, it has heretofore failed to disclose or suggest the specific combination of peroxyacid compounds with chelating agents of the type which form substantially water-soluble compounds or complexes with metal cations in the aqueous wash solution, the use of such type chelating agents being solely disclosed in combination with peroxygen compounds used alone or in combination with activators. Moreover, the beneficial effect attendant to the combination of such chelating agents with monoperoxyphthalic acid and/or a water-soluble salt thereof, in particular, is unappreciated in the prior art.